Experimental Study On Oil Displacement Of Heterogeneous Composite System

After years of polymer flooding development in Daqing Oilfield,the horizontal and vertical heterogeneity has been further strengthened,and favorable seepage channels have generally developed,resulting in inefficient and ineffective circulation of injected fluid.In response to this problem,the pre-crosslinked gel particles(PPG)independently developed by Daqing Exploration and Development Research Institute were used to compound with the ternary composite system to construct a heterogeneous composite flooding system suitable for severely heterogeneous oil reservoirs.The overall synergistic effect is exerted.While realizing the plugging of large pores,the swept volume of medium and low permeability layers is enlarged,the oil displacement efficiency is improved,and the recovery factor is further greatly improved after the polymer flooding is realized.In this paper,a three-layer thickening heterogeneous physical model,a long core model and a sand-packing tube model are specially designed for the reservoir physical parameters of a class of oil layers in Daqing Oilfield,which lays the foundation for laboratory physical simulation experiments.The injectability of three kinds of PPG particles was evaluated by the long core flooding experiment;the three kinds of PPG particles were screened by the three-pipe parallel experiment to evaluate the compatibility and plugging of PPG particles with the oil layer;by testing the viscosity and concentration of the three polymers The relationship optimizes the molecular weight of the polymer,and at the same time evaluates its viscosity;through the interfacial tension evaluation experiment,the content of petroleum sulfonate and alkali is optimized;through the indoor static experiment,the stability of the heterogeneous composite system is evaluated;through one-dimensional filling The sand pipe experiment is used to evaluate the seepage performance of the heterogeneous composite system;the optimal concentration and injection amount of PPG and polymer are optimized through the three-layer thickening heterogeneous physical model flooding experiment.Finally,according to the existing experimental basis,a large-scale three-dimensional heterogeneous physical model is used to simulate the actual mine field,and the pressure field analysis and saturation monitoring and comparison are carried out.Change law and oil displacement effect.In this paper,it is concluded that: PPG particles with an expansion ratio of 3 and a particle size of 0.15-0.3 mm are preferred as the best system,and the profile control effect is the best.MPa,the cumulative liquid absorption ratio of the high-permeability layer is 50%,that of the medium-permeability layer is 31%,and that of the low-permeability layer is 19%.The compatibility of PPG particles with the oil layer and the sealing performance are good;The molecular weight of the compound is 25 million as the best system,which has good viscosity;the content of petroleum sulfonate is preferably 0.3%,and the content of alkali is 1.2%;the heterogeneous composite system has good viscosity retention rate;the heterogeneous composite system It has the ability of profile control and plugging control.The process of migration in the core is accumulation-pressure increase-deformation passing-pressure decrease.The injection fluid turns to small pores and expands the swept volume;the preferred PPG concentration in the heterogeneous composite system is 400mg/L,the polymer concentration is 1200mg/L,and the injection volume is 0.5PV;large-scale three-dimensional physical simulation experiments show that: After compound flooding,the seepage field of the medium and low permeability layers changed significantly,the main channels of the medium and low permeability layers widened,and the oil saturation decreased.The enhanced oil recovery value of heterogeneous composite flooding after flooding is 15.8% greater than that of ASP flooding of 10.5%.